Your problem might be in the priority of AND/OR operations. The way your query is constructed, the labels restriction only applies to the Product Requirements project, because the statement between AND operators are resolved first. If issues from other projects have the label you want to ignore, they will show up in your results.

Try to isolate the labels statement using parentheses. Something like this:

TAGS

I have multiple projects that use variations of the same base workflow. The variations depend on the requirements of the project or issue type. The variations mostly come in the form of new statuses ...